Need Help on Solar System

RedNeckSolarMan
RedNeckSolarMan Solar Expert Posts: 34
Hello everyone, I need help on my solar system. What is going on is the batteries are not charging at all. I have two solar panels, one is 60 watts and other is 20 watts. They are wired up to home made fuse box, where wires run to a Morningstar PS-30 charge controller. The 20 watt solar panel has a 2 amp fuse on it for protection. I did take a reading going to charge controller and I am getting about 19-20 volts from solar panels.

I am using two marine batteries for my solar system and both are reading about 11.8 amps. I even tried taking one out of picture and still nothning is getting charged. I am even had the charge controller replaced, (under warranty), thinking charge controller was problem, but I am getting same results. I am using 12 gauge landscape wires for all my wires. I read online people using landscape wire for small solar systems.

If anyone has any ideas or had this happen before, please let me know and thanks.

Comments

  • RedNeckSolarMan
    RedNeckSolarMan Solar Expert Posts: 34
    Re: Need Help on Solar System

    Let me correct something, I stated using home made fuse box, its not, sorry. I am used to saying that alot, its home made combiner box. : )
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need Help on Solar System

    The problem is a common one: not enough panels. You've got 60 + 20 = 80 Watts. On a 12 Volt system you might get 5 Amps of current from them. You're trying to charge two marine batteries which are about 90 Amp hours each. That's 5 Amps trying to charge 180 Amp hours or a rate of 2%. Barely enough to keep up with self-discharge, much less replenish from any load draw.

    The 19-20 Volts you see from the panels is Voc; it means nothing here.
    The 30 Amp charge controller would be able to charge those batteries if it had about 280 Watts of panel connected.
    I do not know what you mean by "two marine batteries for my solar system and both are reading about 11.8 amps". They might read 11.8 Volts (in which case they are badly discharged and may not recover), but Amps is a measure of current flowing from somewhere to somewhere.
  • RedNeckSolarMan
    RedNeckSolarMan Solar Expert Posts: 34
    Re: Need Help on Solar System

    Ok, that makes sense now. Do you think if I drop to one battery and get a lower crank amp battery. The two are same batteries, 845 crank amp batteries from Everstart, and I know they have small marine batteries.

    This seems so weird, this system was working great until last several weeks.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need Help on Solar System

    There's a key problem: "a lower crank amp battery". A battery measured in cranking Amps is not really suitable for deep discharge that comes with RE applications. These Marine "deep cycle" batteries are basically automotive batteries with thicker plates. Not actually designed for repeated cycling despite what they say.

    Even so, that will not change the fact that 80 Watts of panel would only properly recharge about 50 Amp hours of battery, which isn't much (maybe 300 Watt hours if you're lucky). At best it could do one 90 Amp hour battery, but that would be dependent on there being no loads during charging.

    The reason the system seemed to be working up until now is a matter of the discharge finally catching up with the chronic under-charging.

    Since the whole thing needs a re-think, let's go back to the beginning and determine how much load you're trying to run. That will set the size for the battery bank, and that will determine how much PV you need to recharge it.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Re: Need Help on Solar System

    Basically, your controller should be "on" (PV input to Battery output connected). So, if battery voltage is 11.8 volts, then the PV input should be around 12-13 volts maximum (basically, the voltage drop across the charge controller). And that 12-13 volts should be carried back to the solar panel connections themselves. If you see 11.8 volts at the battery and 15+ volts somewhere else between the battery and the solar array, you either have a bad electrical connection or a failed charge controller (which does happen).

    Then you need to measure the current flow--Either reading the display on the controller, or (sorry to keep pushing this) a DC Current Clamp Meter.

    There are other ways of measuring/estimating current flow (open a wire connection and put a DMM in current mode in the circuit--run risk of too much current, or miss-wiring/connecting and causing a short, etc.). Using a DMM set to 2 volt or 0.2 volt scale and measure the voltage drop in a hunk of wire (use the wire length as a shunt, look up the resistance for that length of wire and use I=V/R to solve for current). Install a battery monitor, etc... But the DC current clamp meter is a great tool for diagnosing problems.

    If the charge controller and wiring is all OK and you are pumping current into the battery, then look for loads that are not turning off (parasitic loads). This is a common problem that drains the battery bank, for an otherwise functional PV system, and kill the batteries.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RedNeckSolarMan
    RedNeckSolarMan Solar Expert Posts: 34
    Re: Need Help on Solar System

    Thats good info guys, pretty much this solar system is for to have lights on my balcony at night. I run dc rope lights as my lighting. Normally in past, the lights run between 1.3 - 1.5 amps.
    The one thing I will have to look into is replace the 20 watt panel with something else, but thats way down the road for now.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need Help on Solar System

    1.5 Amps for, say, 12 hours is 18 Amp hours. That would be about 1/10 the capacity of those batteries. That's why it has lasted so long. 80 Watts of panel should be able to supply that too (80 Watts @ 77% efficiency = 61 Watts * 4 hours good sun = 246 Watt hours / 12 Volts = 20 Amp hours). This is assuming DC lights; no inverter to power.

    I'd say your best bet for now is to try and recharge each of those batteries from another source, such as an automotive charger, and see which one comes back closest to full charge. Then check the wiring connections to make sure the panels are putting out to the battery as Bill said. One of those batteries should be enough, and if you can get 5 Amps from the panels it would just do to recharge it without loads.

    But it looks like what you really need is a smaller battery of about 50 Amp hours.
  • RedNeckSolarMan
    RedNeckSolarMan Solar Expert Posts: 34
    Re: Need Help on Solar System

    Thanks guys for info, for now, I replaced one battery with smaller battery and took out the other battery (gave it to someone that owns a boat). Smallest I can get hold of was 100 amp hour battery. I double checked my connections on all points of solar system. I will wait a day or two to see what are the results and take it from there. Thanks again for info.
  • SolaRevolution
    SolaRevolution Solar Expert Posts: 410 ✭✭
    Re: Need Help on Solar System

    How long is the wire run between the PV panels and the battery?
  • RedNeckSolarMan
    RedNeckSolarMan Solar Expert Posts: 34
    Re: Need Help on Solar System

    that's good question, I am estimating about 4-5 feet of wire from panels to combiner box. There is not much wire from combiner box to charge controller and to battery. I gave more wire than usually just in case. But I was thinking of cutting that down and rewire everything to have easier access to combiner box. The combiner box is in small area that is good location, until you need to work on it.